Hi guys, maybe you have figured it out yet, but if not, here is my solution:
I had the same 'net usershare' error even if packages 'samba' and 'caja-share' were installed. I found out that my user was not part of the 'sambashare' group. Here is what you should do:
Check if your user is part of the sambashare group as follows:
groups your_username
In my case I was not a part of the sambashare group. To add your user in this group, run the following:
sudo usermod -a -G sambashare your_username
Then, logout or reboot and everything should work fine.